A change in the way paramedics treat cardiac arrest patients could delay their arrival to the hospital, but also could increase their chances of survival.

New protocols released by the Maryland Institute for Emergency Medical Services Systems create two major practice changes for EMS providers. As of July 1, providers must first treat medical cardiac arrest patients on the scene, rather than rushing them to a hospital.

They also now have the authority to declare a patient dead on the scene.

“The public expects that we swoop in, we scoop up the patient, and we swoop out,” said Alan Butsch, battalion chief for the EMS section of Montgomery County Fire & Rescue Service.

Now, EMS providers are required to perform “high-quality continuous CPR” for 15 minutes on the scene. If a patient regains cardiac activity during that time, the patient would be taken to a hospital.

The prior practice in Montgomery County was to get the patient to a hospital as soon as possible, Butsch said.

“We now know that their best chance of survival comes within that 15-minute window and that it depends on effective CPR (which you cannot do when moving the patient) in combination with the advanced techniques our paramedics can do,” Butsch wrote in an email.

Cardiac arrest survival rates are already very low. Nationally, there are roughly 383,000 cardiac arrests that occur outside a hospital each year, and fewer than 8 percent of the patients survive, according to the American Heart Association’s website.

Successful treatment is a race against time. The American Heart Association calls this the “chain of survival” — noticing a cardiac arrest and calling for emergency help, early CPR, defibrillation, “advanced life support” and proper care afterwards.

The first steps in this chain, medical officials said, might be the most crucial.

“If we are going to save them, we are going to save them right there,” said Richard Alcorta, the state EMS medical director at MIEMSS. “For every minute that someone is in arrest with no CPR, the chance of saving them drops by 10 percent.”

After 15 minutes of CPR, EMS providers also can now declare a patient deceased and stop resuscitation attempts if the cardiac arrest did not occur while they were on the scene and the patient does not have a “shockable rhythm” — that is, the person won’t be revived with a defibrillator.

In other cases, EMS still can stop resuscitation, but only after consulting with a doctor.

There are exceptions. EMS providers cannot terminate resuscitation for minors, pregnant women or those with cardiac arrest due to hypothermia or submersion. Families also can request that a patient still be taken to a hospital, Butsch said.

The focus of the new protocols is on patient care, but there is always a risk to consider when ambulances move through traffic with sirens and lights on.

In an emailed statement, the American Heart Association wrote, “In short, staying on the scene can reduce unnecessary transport to the hospital, reduces road hazards during the transport, reduces EMS exposure to biohazards, and reduces the need for Emergency Department pronouncement.”

Statewide, 182 crashes were reported to police involving an ambulance or emergency vehicle in an emergency situation in 2011 and 239 in 2010, according to a University of Maryland, Baltimore analysis of Maryland Automated Accident Reporting System data.

Although these protocol changes affect the behavior of paramedics, medical officials emphasized that the moments before they arrive count as well.

“The patients that do better are the ones who had bystander CPR,” said Kiersten Henry, a cardiac nurse practitioner at MedStar Montgomery Medical Center. “If you don’t know how to do hands-only CPR, learn it.”